Disputation: Christian Zimmermann
Doctoral candidate Christian Zimmermann at the Department of Physics, Faculty of Mathematics and Natural Sciences, is defending the thesis
"Revealing the Origin of electrically-active Defects in β-Ga2O3 and r-TiO2 "
for the degree of Philosophiae Doctor.
“The thermoelectric effect in semiconductors and its use in materials characterization and device applications”
Defects in Titanium Dioxide and Gallium Sesquioxide
Semiconducting materials are instrumental for the transition to a carbon-free society. Materials, such as titanium dioxide (TiO2) or gallium sesquioxide (Ga2O3) are promising for a number of applications in energy harvesting and conversion. TiO2 can be used to produce hydrogen from sun light and waste water, whereas Ga2O3 promises more efficient devices for electricity conversion. All semiconductors contain small amounts of microscopic imperfections (defects) which have a pronounced influence on the properties of the material. For example, defects influence what color of light a material absorbs or how well it will conduct electrical current. Often, it is challenging to identify the specific defects being present in a material. In this PhD project, a variety of experimental techniques were used to reveal the origins of specific defects being present in TiO2 and Ga2O3. Some of the identified defects are shown to be highly relevant for applications of the materials. Moreover, it is demonstrated how the formation of certain defects which are detrimental for applications can be promoted or suppressed.